1. Field of the Invention
The present invention relates to a backlight unit of a plane display, and more particularly, to a backlight unit for changing lamps therein conveniently.
2. Description of the Prior Art
Backlight units are known in the art. The backlight unit, which is a key element in the fabrication of liquid crystal displays, is widely used in digital cameras, PDAs, vehicle satellite navigation systems, computer monitors, flat panel TVs and so on. Typically, a backlight unit, which is generally installed underneath a display panel, comprises a light source (or multiple light sources) and a light diffusion means for providing a uniformly distributed light source. According to the position of the light source, backlight units are typically divided into two major categories: edge light type and direct-type, wherein the direct-type backlight unit can provide higher intensity of light and is thus more suited for large size display panels, such as display panels or TV panels, than the edge light type.
Referring to FIG. 1 of a cross-sectional diagram of a direct-type backlight unit according to the prior art, a display 10 includes a display panel 12, an optical sheet composed of a diffuser sheet 14 and a prism sheet 16, and a diffusion plate 18 positioned on a backside of the display panel 12. A plurality of lamps 20 are positioned within a bottom frame 26, and a reflecting sheet 22 is positioned on an inner surface of the bottom frame 26. The bottom frame 26 is combined with a top frame 24, so as to fix the display panel 12 with the underneath elements of the backlight unit.
The reflecting sheet 22 reflects light from the lamps 20 to improve light utility. The diffusion plate 18 diffuses the reflected light into uniformly distributed light. Normally, the diffusion plate 18 is made of acrylic or polycarbonate (PC) materials with a transmittance of approximately between 50% and 80%. In order to provide more uniform light, a surface of the diffusion plate 18 can be further printed with inks to form distributed dots thereon. The diffuser sheet 14 is made of polyethylene terephthalate (PET) or polycarbonate materials with a thickness of approximately between 0.11 and 0.15 mm. The prism sheet 16 is made of polyester or polycarbonate materials to collect light and thus enhance front brightness of the display.
Since the backlight unit has heat radiation problems and the users always demand longer and longer product lifespan to the displays, it is not easy to ensure that each lamp within the backlight unit has the same lifespan. When one of the lamps is broken, it is necessary to prepare tools such as a screwdriver to separate the display panel, the diffuser sheet, the prism sheet and the diffusion plate from the backlight unit individually and carefully to change a new lamp. The procedure of changing the new lamp is not only very troublesome but also possible to result in device pollution or destruction to affect the quality of the display. Sometimes the users may directly change the entire backlight unit because of not knowing how to change the lamps within the backlight unit, resulting in unnecessary waste.